Some charts from 4/3/74

[Chinook]

 A while ago, I downloaded these ECMWF-ERA reanalysis charts of 4/3/74.

500mb heights show a strong closed low in Kansas, with high wind flow (18z)

 

There was CAPE up to 2400 J/kg in the South, but less CAPE in the north Ohio Valley, but still enough for severe weather. Normally NCEP reanalysis doesn't show high CAPE values as much as actually happened locally on warm days (this is the ECMWF, so I'm not sure how that performs on this, though)

 

 

 

0-6km of 50 kt to 100kt, as such strong 500mb winds rotated around the trough

 

 

There were dew points of the low 60's to low 70's, with a dryline or cold front type feature, out in front of some 40's dew points in Kansas

 

 

 

 

very low pressure in Iowa, with high low-level winds

 

 

 

0-1km shear values of 30kt to 50kt are a huge component in 0-1km storm relative helicity, highly linked to tornadoes. (large area of 40kt values)

 

[CheeselandSkies]

Shows how the 500mb setup for this outbreak was completely different than the one for Tuesday of this week and why the Super Outbreak comparisons to that were silly. To really get those high-end outbreaks you need to see those very wide E-W, neutral to moderately negatively tilted troughs with a broad area of SW-WSW (not SSW) 500mb flow in the exit region spreading out into the warm sector.